Laser tissue welding refers to techniques by which tissues may be joined in response to exposure to light and the subsequent generation of heat. The goal of these techniques is the rapid joining of tissues with high tensile strength across the union, union throughout the depth of the targeted tissue, a minimum of scar tissue formation, and minimal damage to surrounding tissue. These techniques may also be beneficial in a number of minimally invasive surgical techniques. Laser tissue repair is under investigation or in use in many surgical disciplines for procedures such as closure of skin wounds, vascular anastamosis, occular repair, nerve repair, cartilage repair, and liver repair. Currently, laser tissue repair is accomplished either through welding, apposing two tissue surfaces then exposing to laser radiation to heat the tissues sufficiently to join them, or through soldering, wherein an exogenous material such as a protein or synthetic polymer is placed between two tissue surfaces to enhance joining of the tissues upon exposure to laser radiation. Temperatures greater than 50xc2x0 C. can induce tissue union. This is believed to be induced by the denaturation of proteins and the subsequent entanglement of adjacent protein chains.
In traditional approaches, tissue welding is accomplished when laser light is absorbed by tissue components such as water or hemoglobin, producing sufficient heat to cause denaturation of collagens and other proteins with subsequent entanglement of adjacent protein chains (Guthrie, 1991). The laser light used in this traditional approach does not discriminate between the wound surface and other tissue. As a result, the success of laser tissue welding has been limited because of (1) the generation of superficial welds with poor mechanical integrity as a result of poor optical penetration and (2) excessive damage to adjacent tissues (Bass, et al. 1995; DeCoste, et al., 1992; Robinson, et al., 1987).
Given these limitations, focus has turned to the investigation of exogenous materials to facilitate the transfer of heat to enable wound closure. The exogenous materials used to facilitate laser tissue welding fall into two categories: those selected to preferentially convert light to heat and those selected to facilitate wound closure and healing. Light absorbing materials currently employee include indocyanine green (U.S. Pat. No. 6,221,068, Bass, et al., 1992; Cooper, et al., 2001; and McNally, et al., 1999), India ink (Fried, et al., 2000), and carbon black (Lauto, et al., 2001). Other examples of the use of chromophores, either alone or in combination with other components, include the works of Birch, Cooper, McNally, Sorg and others. The second class of compounds, commonly referred to as solders, has the primary task of facilitating tissue bonding and healing, and is principally used in conjunction with light-absorbing materials as described above. Ranging from viscous solutions to semi-solid pastes, solders are typically made from biocompatible materials like albumin (Wider, et al., 2001; McNally, et al., 2000; Menovsky, et al., 2001; Lauto, et al., 2001; Zuger, et al., 2001; Bleustein, et al., 2000; Poppas, et al., 1993), albumin with hyaluronic acid (Kirsch, et al., 1997; Ott, et al., 2002), fibrinogen (Wider, et al., 1991), collagen (Small, et al., 1997), cellulose (Bleustein, et al., 2000) or chitosan (Lauto, et al., 2001). From these studies it can be ascertained that the primary duties of a solder are to keep dyes immobile when applied in vivo and to provide a sealant across uneven wound edges.
The use of the nanoparticles of the present invention over chemical chromophores is desirable due to the ability to achieve stronger optical absorption and heat generation, the opportunity for tunable absorption, potentially better biocompatibility, and the ability to better target binding to specific cells or tissues.
In many applications, it is desirable to target cells and tissue for localized heating. The therapeutic effects range from the destruction of cancerous cells and tumors, to the therapeutic or cosmetic removal of benign tumors and other tissue. Techniques which effect precise localized heating and illumination would allow one to enjoy therapeutic and diagnostic benefits, while minimizing the collateral damage to nearby cells and tissue. It is desirable that such techniques be amenable to both in vitro and in vivo therapeutic and diagnostic applications of induced hyperthermia and imaging, respectively, of cells and tissue.
A potentially useful in vivo application of such a technique has been recognized for cancer treatment. For example, metastatic prostate cancer is a leading cause of mortality in American men. Estimates indicate that greater than one in every eleven men in the U.S. will develop prostate cancer. Accurate determination of the extent of local disease is often difficult. Methods for accurately detecting localized prostate disease are greatly needed. In addition, localized prostate cancer is generally treated with either radical prostatectomy or radiation therapy. Both of these procedures are plagued by significant morbidity. Minimally invasive treatment strategies with low associated morbidity are made feasible through such applications and could potentially dramatically improve prostate cancer therapy.
A number of techniques have been investigated to direct therapeutic agents to tumors. These have included targeting of tumor cell surface molecules, targeting regions of activated endothelium, utilizing the dense and leaky vasculature associated with tumors, and taking advantage of the enhanced metabolic and proteolytic activities associated with tumors. Antibody labeling has been used extensively to achieve cell-selective targeting of therapeutic and diagnostic agents. A number of approaches have been taken for antibody-targeting of therapeutic agents. These have included direct conjugation of antibodies to drugs such as interferon-alpha (Ozzello, et al., 1998), tumor necrosis factor (Moro, et al., 1997), and saporin (Sforzini, et al., 1998). Antibody conjugation has also been used for tumor-targeting of radioisotopes for radioimmunotherapy and radioimmunodetection (Zhu, et al., 1998). Currently, there is a commercial product for detection of prostate cancer (ProstaScint) that is an antibody against prostate-specific membrane antigen conjugated to a scintigraphic target (Gregorakis, et al., 1998).
The nanoparticles that are the subject of this invention are amenable to these types of targeting methodologies. Examples of such have been described previously in the following copending patent applications: U.S. application Ser. Nos. 09/779,677 and 09/038,377, and international application PCT/US00/19268, which are fully incorporated by reference as if expressly disclosed herein. The nanoparticle surfaces can easily be modified with antibodies, peptides, or other cell-specific moieties. The utility of these nanoparticles in the localized treatment of disease is a consequence of their photothermal properties. It has been shown that elevated temperatures are useful in joining tissue. (Lobel, et al., 2000; Fried, et al., 1999). Judicious placement of the nanoparticles to the area to be treated, followed by the proper excitation results in a localized heating which forms the basis of the various nanoparticle treatment strategies demonstrated to date.
We now demonstrate that nanoparticles that strongly absorb light corresponding to the output of a laser are useful for another therapeutic application, namely as enhancing agents for laser tissue welding procedures. Specifically, gold-silica nanoshells are designed to strongly absorb light at 820 nm, matching the output of the diode laser used in these experiments. The nanoshells are coated onto the surfaces of two pieces of tissue at the site where joining was desired. Upon exposure to the diode laser, the tissue surfaces are joined when they had first been treated with nanoshells but are not joined under these illumination conditions without nanoshell treatment. Absorptive nanoparticles, such as metal nanoshells, may be coated onto tissue surfaces or may be incorporated into a tissue solder formulation. The nanoparticles offer tunable optical absorption to allow facile matching of nanoparticle absorption to the output of various commercial lasers. Additionally, the technique affords methods to minimize tissue damage by using the least harmful wavelengths of light and/or lower powered light sources.
In the preferred embodiment, a method of joining tissue comprises delivering nanoparticles that absorb light at one or more wavelengths to the tissue and, exposing the nanoparticles to light at one or more wavelengths that are absorbed by the nanoparticles. In the preferred embodiment, the light is laser light although it may alternatively be non-laser radiation. It is also preferred that the nanoparticles used be nanoshells. In a specific embodiment, the nanoparticles are metal nanoshells. Alternatively, the nanoparticles are metal colloids, such as gold colloid or silver colloid. In another embodiment, the nanoparticles may be fullerenes. In the preferred embodiment, all of the nanoparticles are of the same composition; however alternatively, the nanoparticles may be of more than one composition. In the preferred embodiment, the light is infrared light; in alternative embodiments, the light may be visible or ultraviolet or any combination of infrared, visible, or ultraviolet light. In a specific embodiment, the light is red to near-infrared and is in the wavelength range of 600-2000 nm. In a preferred embodiment, the light is near-infrared light and is in the wavelength range of 700-1200 nm. Most preferably, the light is in the wavelength range of 750-1100 nm. The nanoparticles have dimensions of between 1 and 5000 nanometers. In the preferred embodiment, the nanoparticles have dimensions of between 1 and 1000 nanometers.
In a specific embodiment, at least a portion of the nanoparticles is mixed with one or more proteins. Specific embodiments of protein/nanoparticles systems include nanoparticles mixed with albumin, fibrinogen, collagen, elastin, fibronectin, laminin, chitosan, fibroblast growth factor, vascular endothelial cell growth factor, platelet-derived growth factor, epidermal growth factor, or insulin-like growth factor or combinations thereof. Alternatively, at least a portion of the nanoparticles may be mixed with one or more polymers. Specific embodiments of polymer/nanoparticle systems include nanoparticles mixed with polyethylene, polyethylene glycol, polystyrene, polyethylene terephthalate, polymethyl methacrylate, or combinations thereof. In another embodiment, at least a portion of the nanoparticles is mixed with one or more polymers and one or more proteins. In a specific embodiment, at least a portion of the nanoparticles is bound to a chemical moiety. In a specific embodiment, at least a portion of the nanoparticles is bound to an antibody.
In another embodiment of the invention, a method of joining tissue to non-tissue material comprises delivering a first set of nanoparticles that absorb light at one or more wavelengths to tissue, delivering a second set of nanoparticles that absorb light at one or more wavelengths to non-tissue material, and exposing the first set of said nanoparticles and the second set of nanoparticles to light at one or more wavelengths that are absorbed by the first set of nanoparticles and the second set of nanoparticles. In the preferred embodiment, the sets of nanoparticles are of the same composition. Alternatively, the sets of nanoparticles may be of different composition. In the preferred embodiment, the nanoparticles in the tissue and non-tissue absorb light at at least one common wavelength. Alternatively, they may absorb at different wavelengths. In the preferred embodiment, both sets of nanoparticles heat up simultaneously, thereby exhibiting the same heating profile. In alternative embodiments, the heating profiles may be different. In specific embodiments, one or both of the sets of nanoparticles are mixed with protein, polymer or a combination thereof. In the preferred embodiment, the light used is laser light, however, in an alternative embodiment, the light may be non-laser radiation. In a specific embodiment, the non-tissue is a medical device. In another specific embodiment, the non-tissues comprise engineered tissue.
In a specific embodiment of the present invention, a method for reducing wrinkles or other cosmetic defects such as stretch marks in tissue comprises delivering nanoparticles that absorb light at one or more wavelengths to the tissue and exposing said nanoparticles to light at one or more wavelengths that are absorbed by the nanoparticles. In other specific embodiments, methods for cosmetic or therapeutic laser resurfacing of tissue are used.
In another embodiment of the present invention, a method of heating tissue comprises delivering nanoparticles that absorb light at one or more wavelengths to the tissue and exposing the nanoparticles to light at one or more wavelengths that are absorbed by the nanoparticles. Nanoparticles may be delivered to the tissue in a formulation containing a protein or polymer. In a specific embodiment of the invention, tissue is ablated by the method. In another embodiment, coagulation of blood is induced by the method.
In another embodiment of the invention, a method of joining non-tissue materials comprises delivering nanoparticles that absorb light at one or more wavelengths to one or more of the materials, exposing said nanoparticles to light at one or more wavelengths that are absorbed by the nanoparticles. Nanoparticles may also be embedded within one or both non-tissue materials. In a specific embodiment, the non-tissue materials are polymers, such as polyethylene, polystyrene, polyethylene terephthalate, or polymethyl methacrylate. In this application, nanoparticles are intended to absorb light and convert it to heat in order to raise the temperature of the material to near or above the melting temperature. This increases the mobility of polymer chains, allowing chains from the adjacent materials to become entangled and for the materials to become mechanically interdigitated, thus forming a union between the two materials. Ideally, the nanoparticles would absorb light at a wavelength where absorption of light by the polymer is low so that heating will be localized to the region where nanoparticles are present. This can minimize the appearance of the joint between the two materials. Additionally, such an approach can minimize the size of the joint between two materials, which may be advantageous in microfabrication or other fabrication processes.
In a preferred embodiment, there is a method of joining tissue comprising the steps of delivering nanoshells to the tissue, the nanoshells having a light wavelength extinction maximum between 750 and 1100 nanometers, and exposing the nanoshells to light at wavelengths between 750 and 1100 nanometers.
In a specific embodiment of the method, at least a portion of said nanoshells is mixed with one or more proteins. In another specific embodiment, the one or more proteins is selected from the group consisting of albumin, fibrinogen, collagen, elastin, fibronectin, laminin, chitosan, fibroblast growth factor, vascular endothelial cell growth factor, platelet-derived growth factor, epidermal growth factor, or insulin-like growth factor and combinations thereof.